Synthesis and Properties of In-Situ Bulk High Impact Polystyrene Toughened by High cis-1,4 Polybutadiene

A series of high impact polystyrenes (HIPS) were successfully prepared by in-situ bulk polymerization. Selective polymerization of butadiene (Bd) in styrene (St) was achieved by using a neodymium bis(2-ethylhexanol)phosphonate/diisobutyl aluminum hydride/diethylaluminum chloride (Nd(P(507))(3)/Al(i-Bu)(2)H/AlEt(2)Cl) catalyst, affording a prepolymer with high cis-1,4 content of 96.6% and extremely low styrene content of 1.01%. The prepolymer solution was further subjected to the radical polymerization of styrene to produce HIPS. The impact strength of HIPS increased from 48.5 to 166.2 J/m, with an increase of rubber content from 5% to 15%, whereas the tensile strength at break decreased from 17 to 12.5 MPa. Moreover, the impact strength and the tensile strength at break of HIPS increased from 72.4 J/m to 120.6 J/m and 13.2 to 16 MPa, respectively, as the initiator concentration decreased from 0.05% to 0.01%. HIPS showed the highest impact strength of 84.8 J·m(−1) and displayed well “salami” morphology when using a trifunctional 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane initiator.